Christopher rode his bike for $3$ kilometers on each of the past $5$ days. How many kilometers did Christopher ride his bike altogether?
Explanation: The total number of kilometers biked is the product of the number of kilometers biked each day and the number of days that Christopher went biking. The product is $3\text{ kilometers per day} \times 5\text{ days}$ $3\text{ kilometers per day} \times 5\text{ days}= 15\text{ kilometers}$ Christopher biked a total of $15$ kilometers.